1. Field of the Invention
The present invention relates to a toner for developing a latent electrostatic image in electrophotography, electrostatic recording, electrostatic printing or the like, a developer using the toner, a toner container for containing the toner, a process cartridge using the toner, an image forming apparatus using the toner, and an image forming method using the toner.
2. Description of the Related Art
Electrophotography uses a developer to develop a latent electrostatic image formed on a latent electrostatic image bearing member. Such a developer can be classified into two types: a one-component developer consisting of toner, and a two-component developer consisting of carrier and toner. The two-component developer can provide relatively stable, excellent images by mixing carrier and toner together to allow toner particles to be positively or negatively charged.
Toner production process can be broadly divided into two general categories: dry process, and wet process. In the former process, a binder resin, a colorant, a releasing agent, etc., are melted and mixed together by heat and pressure, cooled, and pulverized into toner particles. Since this pulverization process involves smashing of toner particles into a plate by means of air pressure and collision of toner particles, finely pulverized toner particles are not spherical and have irregularities.
In the latter process, a binder resin, a colorant, a releasing agent, etc, are added to a solvent for polymerization, followed by drying to produce toner particles which are therefore spherical and have smooth surfaces.
Along the widespread use of color-image forming apparatus of recent years, small diameter toners are under study for high-definition color images.
For the production of small diameter toners, wet process is more advantageous than dry process. Wet process, however, tends to produce spherical, smooth toner particles as described above, resulting in poor removability. In particular, cleaning troubles occur frequently in the case of blade cleaning. Against this background, a number of proposals have been under study to control toner shape in wet process.
For example, Japanese Patent Application Laid-Open (JP-A) No. 11-174731 discloses a toner that comprises toner particles and an external additive and has the following characteristics: average circularity=0.920 to 0.995; weight-average particle diameter=2.0 μm to 9.0 μm; the proportion of particles with an average circularity of less than 0.950 is 2% to 40% on a number basis; and the external additive is present on the toner particles in the form of primary particles or secondary particles.
Japanese Patent Application Laid-Open (JP-A) No. 2000-214629 discloses a toner composed of toner particles, where a coefficient of variation for shape coefficient is 16% or less and a coefficient of number variation in the number-based size distribution is 27% or less.
Japanese Patent Application Laid-Open (JP-A) No. 2000-267331 discloses a toner that comprises resin particles and a colorant and satisfies is the following conditions at the same time: GSDv≦1.25, SF=125 to 140, D50v=3 μm to 7 μm, (the proportion of particles with SF-1 of 120 or less)≦20% on a number basis, (the proportion of particles with SF-1 of 150 or greater)≦20% on a number basis and (the proportion of particles with SF-1 of 120 or less and a circle equivalent diameter of ⅘ or less)≦10% on a number basis.
Japanese Patent Application Laid-Open (JP-A) No. 2002-62685 discloses an image forming method using a toner where a coefficient of variation for shape coefficient is 16% or less, a coefficient of number variation in the number-based size distribution is 27% or less, and a toner flocculation ratio is 3% to 35%.
It is, however, difficult for the strategies disclosed in these Patent Literatures to provide high-definition images and to achieve long-term stable removability. More specifically, toner particles with specific shape factors specified by these conventional techniques cannot be removed well with a blade cleaning approach. Furthermore, there is a problem that cleaning troubles occur, particularly in a case where smaller toner particle diameters are employed along with the recent demand for high-quality images and where toner particles have smooth surfaces without irregularities.
Thus, toners that can provide long-term removability and high-definition images with reduced image layer thickness and densely-packed toner particles, and related technologies using such toners have not yet been provided.